2026 Workshop Handout Bundle-W126D - QSART Clinical Applications and Pitfalls

W126D - QSART Clinical Applications and Pitfalls - Khalid

Pdf Summary

QSART (Quantitative Sudomotor Axon Reflex Test) measures postganglionic sympathetic cholinergic function by recording sweat production after acetylcholine is delivered through the skin. It is commonly used in autonomic testing, particularly to assess small-fiber neuropathy, which may be present even when routine nerve conduction studies are normal.<br /><br />Clinical uses include evaluating diabetic, idiopathic, amyloid, autoimmune, and hereditary neuropathies; characterizing autonomic failure; assessing autoimmune autonomic disorders; identifying the neuropathic subtype of POTS; and monitoring selected conditions over time. Patterns can help guide interpretation: reduced sweating distally may indicate length-dependent neuropathy, widespread reduction may suggest generalized autonomic failure, and absent responses may reflect severe postganglionic dysfunction. Normal QSART alongside an abnormal thermoregulatory sweat test can point toward a central or preganglionic problem.<br /><br />Results require caution. Medications that suppress sweating, environmental conditions, age, hydration, cold extremities, and technical problems can distort measurements. A normal result does not rule out small-fiber neuropathy, since sensory and autonomic fibers may be affected differently. QSART also samples only a few sites, so focal disease may be missed, and it is not designed to localize central lesions.<br /><br />QSART is most informative when interpreted alongside the patient’s symptoms and examination, other autonomic tests, thermoregulatory sweat testing, or skin biopsy. Its diagnostic value lies in the pattern of findings and their integration with broader clinical data—not in treating a result as simply normal or abnormal.

Keywords

QSART

Quantitative Sudomotor Axon Reflex Test

postganglionic sympathetic cholinergic function

small-fiber neuropathy

autonomic testing

diabetic neuropathy

autonomic failure

POTS

thermoregulatory sweat test

skin biopsy